A Sydney Catholic nun and teacher killed in the airline disaster in the Ukraine was returning from a French retreat.

NSW Premier Mike Baird released a statement on Friday night saying there are now three confirmed passengers from the state that were on board Malaysian Airlines flight MH17 that was shot down by a surface-to-air missile near Ukraine's border with Russia.

He did not name the last two confirmed victims.

We are devastated by the loss of such a wonderfully kind, wise and compassionate woman who was greatly loved by us all.

Kincoppal, Rose Bay, principal Hilary Johnston-Croke

Sister Philomene Tiernan, a teacher at eastern Sydney Catholic girls' school, Kincoppal-Rose Bay, School of the Sacred Heart, was returning home from attending a retreat in Joigny in France.

In a letter to students, principal Hilary Johnston-Croke said the school was devastated by the loss of Sister Philomene.

"Phil was a very much-loved staff member and friend," she said.

"She contributed greatly to our community and she touched the lives of all at KRB in such a positive and meaningful way.

"We are devastated by the loss of such a wonderfully kind, wise and compassionate woman who was greatly loved by us all. She was great friend and mentor to me personally."

"The first thing you think about her is an incredibly gentle personality ... one of those blithe gentle spirits that you never touch without coming away a little bit enriched," he told Richard Glover on 702 ABC Sydney.

"While she [was] not teach young women at the moment, she's been involved in getting them into reflection and meditation.

"Her contact with young women up at Kincoppal was powerful."

Premier Mike Baird has sent his condolences to the victims' families and friends.

“The deaths of any Australians in these circumstances strikes us to our hearts, but we grieve with extra force where they were our neighbours, our friends, the people who helped build and nurture our communities," he said.

And Federal Communications Minister Malcolm Turnbull tweeted that his wife Lucy and daughter Daisy had been inspired by Sister Philomene.

You have no doubt been hearing a lot about the Paris Agreement and know that it pertains to climate change, but are too embarrassed at this stage to ask for an overall explanation of what it's all about.